In the field of semiconductor manufacture there is often a need to de-process a semiconductor die by removing layers, which can be from several thousand angstroms (Å) thick to less than 100 Å thick, one at a time from the surface of the die. For example, de-processing a die aids in determining device failure mechanisms and is also useful in determining patent infringement of a competitor's part.
Current methods of die de-processing include removal of layers using a portable hand polisher such as those available from Buehler of Lake Bluff, Ill. and Allied of Rancho Dominguez, Calif. To use these polishers for die de-processing, the back (noncircuit side) of a semiconductor die is adhered to a generally planar support such as a “puck” with an adhesive such as pine tar. An abrasive pad, for example a material comprising a diamond lapping film, is mounted to a planar platen of the polisher. The polisher is activated and the abrasive pad is contacted with the circuit side of the die to remove layers therefrom.
Various problems result from this method of die de-processing. For example the leading edge of the die which first contacts the abrasive pad is removed at a faster rate than the remainder of the die. This results in more difficult data analysis than if the surface of the die is removed more uniformly.
Another de-processing method includes the removal of layers with an acid, but this method suffers from lack of control in chemical migration from one metal layer to another. Further, acid etches are not planar as various materials are etched at varying rates.
A method and structure for de-processing a semiconductor die which reduces or eliminates the problems described above would be desirable.